UMO+ First layer varying between too low and too high

[veedee 4]

Fellow makers,

I produce parts that have to be pretty much identical each time. I make about 600-1000 of these parts each week. But I constantly run into a first layer extrusion problem. The problem occurs on all my UMO+ machines (5 of them)

What happens is: the first layer is either to high causing under-extrusion and sticking issues, or to low causing over-extrusion and material smearing issues. It varies between each print run. So on the same machine, the first layer on the printrun 1 can be too high, but the first layer on printrun 2 can be to low. It happens with the identical gcode, as well as between different gcodes.

I feel like the mechanical Z-endstop is affected by the temperature in some way. Or the printbed expands/contracts with different temperatures causing it to bend very slightly. The ambient temperature varies somewhere around 22-28 ºC, depending on the outdoor temperature.

Each time I have to wait for the printer to lay down the first layer of all the 12 parts in 1 printrun, to see if I have to adjust the bed levelling screws. Sometimes having to stop the print and restart. Very tedious, time consuming and frustrating with multiple printers.

Is there anybody who also run into this problem and has a possible fix for it?

[neotko 1,391]

The first thing that comes to mind is to change the endstops to something more precise. @amedee did a great mod using a different endstop that most probably will give you better repetition.

https://www.youmagine.com/designs/software-adjustable-bed-leveling-on-umo